Dad's Army (1968)

Season 4: Episode 5

The platoon is to guard a POW camp housing Italian soldiers and Mainwaring is suspicious because Walker seems rather too friendly with them. However, Walker explains that he uses them as cheap labour to mend radios and they go backwards and forwards in and out of the camp via a tunnel which they have dug beneath the stove. When an inspection is called for and only half the prisoners are available, Jones, doing the head count, makes them go round twice but the plan is rumbled when the missing half turns up.